An Unique Region 185 



It is interesting to note that at the head of North Fork of 

 Bishop Creek is Piute Pass, through which a trail crosses over 

 to the westward-flowing waters of the San Joaquin. This gap 

 or notch in the main divide of the Sierra range was cut by ice 

 of two cirques, one on either side of the divide. The ice of 

 each cirque basin cut back until the wall separating the two 

 cirques was completely obliterated. 



The canyons in the eastern slope of the Sierra Nevada have 

 been heavily glaciated. Glaciers in time past have moved 

 down the gullies from the crest of the range, and tremendous 

 moraines now flank the sides of valleys that come into Owens 

 Valley from the west. Far up the steep slope, along the high 

 crest of the range, glaciers form today in cirques among the 

 high peaks. These are tiny miniatures of the glaciers that ex- 

 isted here during the glacial period. Two epochs of glaciation 

 are recognized as having occurred on the Sierra Nevada escarp- 

 ment during the Quaternary period, the two epochs being 

 separated by a long interval of time. The earlier glaciation was 

 the more extensive and endured for a much longer time. Mo- 

 raines of the earlier glaciation reach down the valleys to alti- 

 tudes of 6,000 to 6,500 feet, or half way from the crest of the 

 range to the present floor of Owens Valley. Many glaciers, 

 however, did not reach the mouths of their canyons, and in 

 consequence many canyons show profound contrasts between 

 their upper portions and their unglaciated lower portions. The 

 lower stretches of the great canyons are deep clefts that are no 

 wider at their bottoms than the streams by which they have 

 been eroded, whereas the glaciated upper portions are wide- 

 floored and generally characteristically U-shaped. 



Marked Difference in Age of Moraines 



The difference in age of the early and later moraines is 

 shown by the degree of weathering and breaking down of the 

 rock fragments that the moraines contain, and by the extent 

 to which streams have cut gullies and canyons in the morainal 



